Purge terminal command for regular Ubuntu

Hi!

I recently switched to Ubuntu Mate on a portable laptop. I started with regular Ubuntu 17.10. However, the graphics card on the unit couldn’t handle the system and memory was tight (only 4GB on this portable). Switched over to Ubuntu-Mate with the following command:

sudo apt install ubuntu-mate-desktop
sudo apt install ubuntu-mate-core *** didn’t need this but read elsewhere to include**

Although I can select Mate as the destkop system on the logon screen how can I purge regular Ubuntu (do they call it Ubuntu-gnome now after Unity?).

Thanks!